Process for extracting helium



@et 4, 932. R. R. BoTToMs 1,881,115

' PROCESS FOR EXTRACTING'HELIUM Filed May 13, 193D ATI'RNEYs Patente ct. 4, 1932 v UNITED sTivn-.s

PATENT OFFICE .'ROIBERL ROGER BOTTOMS, 0F LOUISVILLE, KENTUCKY, ASSIGNOR T0 THE HELIUM COMPANY, F LOUISVILLE, KENTUCKY, A CORPORATION 0F KENTUCKY PROCESS FOR yEX'J.I1!..B.CEITING IEIIELIUINIy VAppueaiion mea may 1a, i930. serial No. 452,020.

This inventionj relates to the separation of helium from other gases which have boiling points,l at atmospheric pressure, above' ther critical temperature of helium. The invention is likewise applicable to the separation of neon from the same kind of gases, and therefore for t e purposes of this invention, neon is to be considered as the equivalent of helium.

'processes 1n which expansion, rectification,-

The main object xof the present invention is to eect the separation and removal ofthe helium, in a substantially pure state and as a single step, as distinguished .from previous recompression and other such series of steps are employed. V

In commercial practice it is customary after extracting the'helium to store it in' st'eel cylinders under comparatively high pressure, for instance 2000 pounds per square inch.

This invention is an improvement on that disclosed in my previous Patent 1,821,540,

issued. Sept. 1, 1931, in which crude helium is circulated in a closed cycle in two pressure stages, both substantially above that of the atmosphere, and the pure helium is withdrawn from the'higher pressure stage of the cycle in gaseous form and substantially hehum-free liquid is withdrawn from the cycle from the lower pressure stage, the cycle being continuously replenished by the addition of f further mixture from which the helium is to be extracted.

i .In the specific embodiment disclosed in sald patent, this'mixtureis rst compressed and largely if not completely liquefied and the crude helium separated therefrom for circulation in said cycle.

My present invention is an im rovement a-nd simplification of that speci cally disclosed in said patent in that I add the mixture in gaseous state directly to the crude helium gas in the cycle, and liquer'y .all of the nonhelium constituents in 'the' cycle instead of before they enter the cycle. Thus I may use gases containing a very low percentage of x helium and the percentage in the crude helium is gradually built up to a concentration where' vonlya portion ofthe helium will go into solu tion upon the liquifying ofthe readily liqueiable portions of the crudehelium under high pressure in the cycle, and pure helium gas may be directly separated at high pressure and delivered for storage. Thus all of the compression may take place solely in the crude helium cycle and the necessity for separate compression of the' gaseous mixture serving as the' source of supply is avoided.

lOther ob]ects, advantages and important features of my invention will be pointed out hereinafteror will be apparent from a consideration of the following description and the accompanying drawing showing a preferred embodiment. Q

f As an example of the gas which may be treated by my process, I may mention a natural gas which after the removal of all carbon dioxide and water, has the following compsitionz-helium 2%, methane 20%, ethane v 2% and nitrogen 7 6%.- Any other helium containing gas freed of carbon dioxide and lwater' vapor may be used.

In the drawing, the single view is a vertical u heat of compression is removed. The gas isA then delivered through the pipe I4c in a heat .interchanger 1, thence through a'pipe 1l to a coil 6 in the chamber 3 of a condenser, to a collecting pot or chamber 15 in the lower part of the condenser.

It must be understood at this point that the operation has just started, and that the ressure is graduallybuilt up to this point y a compressor 232' I When the pressure in the parts 'before named hasl reached a value of approximately 2000 pounds, valve 8 is opened andrthe g'as is v at the approximate value of 2000 pounds. In

throttling the gas from the high pressure through valve 8 it suers a drop in temperature by the well known Joule-Thompson efd fect. From yreceiver2 the cooled gases pass through valve 9 and pipe 12'through chamber 3 of condenser 7 and thence through pipes 10and passage 5 in heat interchanger l, and

to the atmosphere, or when. it is desired to save the gas, into a pipe line through pipe 19.

The gases which have been cooled by the Joule-Thompson eect in throttlingV through valve 8, in their passage through the heat interchanger 1, counter-current to the ingoing gas in pipes 4, take up the heat from the ingoing gases in pipe 4, and cool,these gases to a lower temperature.

Subsequently the gases iowing through pipe 11, coil 6 and chamber 15, reaching valve 8have already been cooled to a low temperature and thus suier a `further drop in temperature until a point is finally reached where the gases otherthan helium reach the liquefaction point, which for nitrogen is approximately minus 195 C. 'During this preliminary cooling period valve 24 remains `closed, preventing the escape of the gases through valve 24'and pipe 20. When this point is reached, gases will be liquefied in coil 6 and chamber 15, and since the helium content of the gas is only` 2% the helium itself will be carried in the liquid, that is, in solution with the other liquefied gases. When this liquid is then throttled through valve 8 into the chamber 2, due to the reduction v.in pressure, most `of the helium in solution-will be given off and the pressure of the liquid in receiver 2 will'be maintained at the proper operating point by manipulationo valve 9. This proper operating point is preferably between 50 and 200 pounds pressure. At the valve 9 the pressure may drop vto substantially that of the atmosphere. Avalve 26 in the pipe `16 serves to maintain the desired pressure in the chamber 2, and the delivery. of the crude helium to the compressor at low pressure.

The helium content in the gas will pas's out through pipe 17, thence through pipe 13 in heat interchanger land pipe 16, past valve 26,back to the intake of the compressor where f it is mixed with a further supply of the incoming natural gas. It lwill he seen that the amount of helium in the gas being compressed by compressor 23 will thus gradually increase l 1n value until the point is reached Where the gas entering the apparatus contains an amount of heliumin excess of the saturation point for the liquefied gases. When this point is reached, namely, approximately 3% helium, all the helium in excess of about-3% will ,pass into pipe 14. Valve 24 is then partially open, suicient to regulate the flow of helium mal operation, and the gases being throttled through valve 8 into receiver 2 carryin soluy tion approximately 3% by volume of helium. l

All of this helium, with the exception of probably 16% to {6%7 will be given ott from the liquid and passed out through pipe 17 as the liquid is being continuously drawn from receiver 2 through valve9 and pipe 12 into chamber 3 of condenser 7.

These liquefied gases will then surround chamber 15 and coil 6, forming the necessary refrigeration for condensing the gases in coil 6. Part of' the liquids in compartment 3 will then be vaporized and the vaporized gas, together with any excess liquid, will pass through pipe 10 and through the heat interchanger in passages 5, giving up their re- Y frigeration to the ingoing gases.

It will be noted that there is no drop inV pressure between the compressor and the manifold 20 except such as is due to flow resistance andthe pure helium is separated and stored by the use of a single compressor and Without either substantial drop in pressure or the necessity for any recompression. For the purposes of this invention helium is considered pure if'iit doesnot contain over l 10% of other gases.

The apparatus is so controlled that the pot 15 may be kept immersed in liquid and the'coil 6 mayalso be kept immersed in liquid, or a lower level of liquid may be maintained as desired. In any event the coil 6 and the pot 15 are kept at a temperature which is thatproduced by the boiling or evaporating of the non-helium constituents of the gas under low pressure existent in the chamber 3. cient to liquefy substantially all of the nonhelium constituents of the original gas' in the coil 6 and pot 15, due to the fact that within the coil and pot the pressure is very high. The gases produced in the chamber 3 pass through the pipe 10 to the chamber 5 of the heat interchanger,1from which they pass out through the pipe 19.

It will, of course, be understood that the drawing shows only a conventional represen.

tation of a heat interchanger and that the various pipes- 13, 4 and 14.may bein the orm of coils or zigzag passages in order to utilize to the maximumextent the 10W temperature of the outgoing gases to cool down the ingoing gases in the pipe 4.

All of the. helium in excess of 3% will pass out through the pipe 14 in unliquefied form, and this 3% will separate out in the receiver 2 as crude helium containing 50% to of helium, and go back. to the compressor for recirculation, so that substantially all of the helium is ,recovered from the original gas, and the helium delivered to the storage passages 21'is of commercial pu- This temperature is suilirity. By commercial purity I mean containing less than 10% of other gases. As above noted, the loss of helium is only-16% to 2U%. -The percentage ofhelium in the crude helium will vary with the pressure in the chamber 2.

My improved process makes possible the separation or" the helium in a commercially pure state in one step\and the storage of" the separated helium under the pressure of the compressor which supplies the crude gas. The receiver 2, instead of serving for the separation of theX crude helium gas as in A the apparatus disclosed in my Patent 1,821,-

540, serves, in thepresent process, merely for the release of the helium in solution. This portion of the helium is not lost, but is vented to the intake of the compressor and recirculated.

The pot 15 provides for the separation of all of the liquids from the Pure helium instead of separation ofliqueied gas from the recompressedcrude helium mixture, as in the prior application above referred to.

lit will be noted that in my invention there is a continuous cyclic flow of crude helium fluid. The crude helium gas iows yfrom the receiver' 2, through pipes 17, 13 and 16, to the compressor, thence through pipes 18 and 4 and coil 6, to the pot 15. Here the gaseous limpurities become liquefied and are delivered to the receiver 2 under lower pressure, and the crude helium escapes from the liquid as it is vpassed into the receiver.

The cycle involves two pressure phases, the higher pressure, from the compressor to the valve 8', and the lower pressure from the valve 8 back to the compressor. Pure helium is continuously withdrawn vfrom the cycle vsa through pipe 14 .and substantially helium free liquid is continuously withdrawn from the cycle through the pipe 12. Makeup fluid is admitted to the cycle through the pipe 22.'

1f the gas delivered through the pipe 22 contains yless than 3% of helium, all of this helium may be dissolved in the liquid in the pot 15 and pass through to the receiver 2. The percentage of helium iowing, out

through the pipe 17 will be very much higherA than that admitted through the pipe 22, so that the percentage of helium in the gas liqueed in the coil 6 will continuouslyincreaseuntil itexceeds 3%, and then the excess will remain asa free gas in the pot 15, and may ow out through the pipe 14.

Thus the apparatus may be operated until a rconcentration is arrived at where free helium may be drawn 0H, and, the plant thereafter may be continuously operated under substantially uniform conditions. The amount of helium flowing out through the pipe 14 will equal the amountl in the crude mixture delivered in'through the pipe 22.

lf the mixture to be treated contains a -comparatively highA percentage of helium, for example 3%,or more, there may be separation in the pot 15 from the beginning of the operation when the temperature of liquefactionof the impurities has been reached. Of course, if the Ipercentage of helium in the gas treated is\ below {5%,the process will not operate at the pressures stated, because of the solubilityof that amount ot helium in the liquid in the receiver 2.

The improved apparatus illustrated is disclosed and claimed in'my'copending divisional application Serial No. 546,244, filed June 23, 1931.

Having thus described my invention, what I claim as new and desire to Patent is:

1. The method of separating helium from a gaseous mixture, including circulating a crude helium mixture. in a continuous cycle having two pressure stages, at least the higher stage being substantially above that of the atmosphere, separating substantially pure heliumv from liquid containing helium in the higher pressure stage and withdrawing it from the cycle, separating substantially heliunrfree liquid from crude helium gas in secure by Letters the lower pressure stage and withdrawin i' it I yhaving two pressure stages, the upper pressure stage being approximately 2000 pounds per square inch and the lower pressure stage being substantially below that of the higher pressure stage, cooling said mixture and thereby separating substantially pure helium from liquid containing helium in said higher pressure stage, withdrawing said pure helium from the cycle under said pressure of' approximately 2000 pounds, separating substantially helium-free liquid from crude helium gas in the lower pressure stage and withdrawing said liquid from the cycle, andy replenishing said cycle by adding said gaseous mixture containing helium to said crude fhelium gas at approximately the point in the cycle where said crude yhelium gas is raised from said lower to said higher pressure.

3. The method of separating helium from a gaseous mixture, including circulating a crude helium mixturein a continuous cycle having two pressure stages, cooling the crude helium in the higher pressure stage to liquefy substantially all of the mixture cycle the unliqueed substantially pure helium, delivering the liquid to the lower pressure stage of the cycle, separating substantially helium-free liquid from crude other than helium, withdrawing from the are helium gas in said lower `pressure stage of the cycle, adding to the crude helium gas further quantities o the gaseous mixture to be separated, returning the same to the higher pressure stage of the cycle, and evaporating the substantially helium-free liquid to effect said liquefaction. l

Signed at Louisville, in the County off Jefferson and'State of Kentucky, this 7th day of May, A. D'. 1930.

ROBERT RGGER BOTTOMS. 

